#include  <stdio.h>

int main(int argc, char *argv[])
{
	double n;
	double sum=0;
	for( int i = 0 ; i < 12  ; ++i )
	{
		scanf("%lf",&n);
		sum += n;
	}

	double avg = sum/12;

	printf("$%.2f\n",avg);
	
}
